Dammed if we do, dammed if we don’t: New World’s biggest freshwater fish at risk

Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

Two of the world’s biggest freshwater fish are in big trouble, come reports from scientists in North and South America.

First up, the genetically distinct Kootenai River population of white sturgeon (Acipenser transmontanus), North America’s largest freshwater fish. This massive monster has been known to reach almost six meters in length and weigh half a metric ton, but its size hasn’t offered it any protection. In fact, it has made it more attractive, and the species has historically been heavily overfished.

The problem in the Kootenai River isn’t overfishing, although it is man-made: Montana’s Libby Dam, built in 1974. The dam prevents the river from the very flooding that used to tell the sturgeon it was time to spawn. Before the dam was built, an estimated 10,000 white sturgeon lived in the river. Now, just 500 remain, and they have not spawned in the wild in 35 years. Oops.

Despite the lack of wild spawning, the fish have not died out, and that’s also thanks to human intervention. The Kootenai Tribe of Idaho periodically restocks the river with farm-raised sturgeon.

The U.S. Fish and Wildlife Service has been trying to save the Kootenai River white sturgeon from extinction for years by adjusting the amount of water that flows through Libby Dam, but last Thursday they announced that all of their recent attempts have failed. They’ll keep trying, though, and will send even more water through the dam this year. But they can’t send too much or they’ll flood local towns.

Amazonian arapaima

Meanwhile, in South America, another of the world’s largest freshwater fishes—in fact, the largest species with scales—is also in danger of extinction, if it even still exists. A paper in the December issue of the Journal of Applied Ichthyology reports that the giant Amazonian arapaima (Arapaima gigas) are threatened by weak and unenforced fishing regulations in Brazil, despite the species’s protected status under the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES).

Arapaima can reach more than four meters and weigh more than 180 kilograms. The fish actually comes to the surface to breathe, leaving it vulnerable to fishing with spears and nets.

Part of the problem with preserving the arapaima is that it has never really been studied, until now. Authors Leandro Castello and Donald Stewart examined several arapaima samples in museums and found that only one of them was actually the Arapaima gigas. "Our new analyses indicate that there are at least four species of arapaima," Castello told BBC News. "So, until further field surveys of appropriate areas are completed, we will not know if Arapaima gigas is extinct or still swimming about."

Castello and Stewart recommend increased monitoring and tighter controls over harvests to protect the multiple arapaima species from extinction.

And tuna, too

As long as we’re talking about giant fish, let’s not forget the endangered bluefin tuna (Thunnus thynnus), which also remains heavily overfished, and as a result commands incredibly high prices on the open market. Last week, a single, 232-kilogram tuna sold for an all-time high of $175,000 to two Japanese restauranteurs—60 percent higher than last year’s record. That breaks down to $21.38 an ounce—almost three dollars more per ounce than the cost of silver. (And by the time it reaches the dining table as sushi, it will be more like the cost of gold.)

But even at those prices, bluefin won’t be on the menu (or maybe anywhere) for very long.

8 Comments

Honestly i think perhaps they should introduce these fish to the Mississippi river, it’s one of the bigger rivers here in America, and I think they might have a chance to survive. besides how awesome would it be to have fish in the Mississippi the size of a small bus?

I disagree with Someone else’s comment because introducing any wildlife to a new habitat almost always ends in disaster. I understand what you are thinking, and I feel that the sturgeon would probably thrive in the Mississippi, but they will likely thrive too much and drive some of the native creatures to the brink. I hope that conversation efforts continue to help all of the fish listed here and more. You go, guys!

I suspect if one reads the original EIS that allowed construction of Libby Dam to proceed, it either ignored or dismissed the potential threat posed for the sturgeon. Since that fundamental basis of its approval has now been proven false, the dam should be removed, plain and simple.

There is this thing called nature. Part of it is natural selection. The unfit die off. Raccoons are not in danger of extinction because they adapted to a changing environment. This is all a natural process and should happen. Reality is not stagnant. Get over it or fail to adapt and die.

Sturgeon are very fit. They have survived over 200 millions of years of dramatic changes. They survived several ice ages! I’d say they are pretty adaptable. However, there’s not much that can adapt to dam.

As far as tuna goes, a commercial vessel now has the capacity to catch in one day what it would take a whole year to catch 20 years ago. Pretty hard to adapt to that.

I’d say that if humans don’t want to be a victim of natural selection, we should conserve our food resources a lot better (I guess that’s a form of adaptation).